The invention concerns a friction vacuum pump with a frame, rotor and housing. In addition, the invention concerns devices that are equipped with a chamber that must be evacuated and with this type of friction vacuum pump.
The current common type of construction of various friction vacuum pumps (turbomolecular pumps, pumps with turbomolecular pumping stages and other friction pump stages) that can be found on the market is known from DE-A-43 14 419. They have a frame, which is equipped with a drive motor and which supports the rotor. In addition, the frame supports the pump housing. The latter surrounds the rotor and stator, as well as the frame to a greater or lesser degree. The housing ensures the arrangement of the named components in relation to one another. Furthermore, its purpose is to precisely center the stator, which is composed of the stator half-ring disks and spacing rings, so that the small space, necessary in regard to friction vacuum pumps, can be maintained. The housing seals the vacuum pump inside from the outside.
Finally, it is equipped with a connecting flange placed on the face, with which the friction vacuum pumps can be attached to devices that have chambers that must be evacuated. Since there are various types and sizes of flanges, the manufacturer of friction vacuum pumps must produce numerous types of friction vacuum pumps and keep them in stock, in order to meet all the application needs of the customers.
Furthermore, it is known from DE-A-43 31 589 that friction vacuum pumps must be provided with several connection openings. Each of them has a different pressure level. These types of friction vacuum pump mainly serve to evacuate particle radiation equipment (e.g. mass spectrometers) with chambers separated from each other by screens, in which various pressures are to be created and maintained during the operation of the particle radiation equipment. This type of application considerably increases the expense of the manufacture of friction vacuum pumps, which are to meet the widest possible range of customer needs, as well as keeping them in stock.
The basic purpose of the present invention is to simplify the adaptation of friction vacuum pumps to the diverse needs of the customers.
According to the invention, this purpose is resolved in that the housing is made up of two housing parts; the first, inner housing is essentially cylindrical in design, surrounds the stator, and is provided with an entry opening for the gases entering the pump, and the second housing has a bore hole that accommodates the first housing with the pump components, which are located inside it. These measures make it possible to divide the functions of the currently common one-piece housing, as described at the beginning, between two housings. The inner housing ensures the arrangement of the individual components of the friction vacuum pump in relation to one another. This creates a friction vacuum pump in the form of a slide-in unit, which can be subjected to many performance tests, e.g. balancing tests. The function of the outer housing is to adapt the friction vacuum pump, which is operational even without the outer housing, to the customers"" applications. It is no longer necessary to manufacture a great variety of types of friction pump, or to keep them in stock; instead one merely needs one or a few universal, compact, operational pump units (slide-in units, cartridges), as well as the outer housings, adapted to the individual needs of the customers"" applications.
A special advantage of the invention is the fact that the construction of the second, outer housing can be left to the customer. It is sufficient to inform the customer of the external dimensions of the slide-in friction pump unit. A very simple solution for him is to provide a borehole in the housing or housing part of his device (equipment, implement, etc. with one or several chambers to be evacuated), into which the slide-in friction vacuum pump unit can be inserted. When ready for operation, the customers"" housing or housing part of the equipment then forms the second, outer housing of the friction vacuum pump according to the invention. This eliminates a separate, expensive, connection housing. In addition, conductance losses can be kept low, due to the connection of the friction vacuum pump close to the chamber, and thus the low chamber pressures, dependent on the process, can be realized. Optimal conductance is attained.